Photography News issue 26

Photography News Issue 26 absolutephoto.com

Technique 61

Photo school Camera class Everyone has to start somewhere, even pros, and in Photo School we look at the core skills every beginner needs. This month, how to use exposure bracketing and how to combine exposures in Photoshop...

Explained Threeways to bracket your exposures

Use exposure compensation The camera’s exposure compensation function allows you to alter the metered values, sometimes by as much as +/-5.0 stops. It’s activated via a button or dial on the camera body. After your first shot, dial in a negative value, shoot, then dial in a positive value. With this method you can use different values (for example 0.0EV, -1.7EV and +2.3EV), so there’s lots of control, but it takes longer and you need a tripod if merging exposures.

Words & pictures by Kingsley Singleton

What is exposure bracketing? Bracketing simply means shooting the same scene multiple times, each with different exposure settings. This is helpful when you’re not sure exactly what exposure you need; such as when the subject is backlit or some parts of the scene are much brighter than others. It means that you have a safety net, and can pick the best shot after the event. Usually bracketing involves a metered exposure, and exposures are taken either side of that value, resulting in lighter and darker versions. Howmuch bracketing is needed? Exposure values – the shutter speed, aperture setting, or ISO level – are measured in ‘stops’ (one stop being thedoublingorhalvingofoneofthose values), and this is how you govern howwidely your bracketed exposure will vary; so, a three-shot bracket at +1.0 and -1.0 stop would give you less variation than a three‑shot bracket at +2.0 and -2.0 stops. The more complicated the light, the more you should vary the difference in exposure, and you can also shoot more frames if desired, recording five, seven or even nine shots to cover it. Shooting many frames to cover the entire range of light also means you can combine the separate exposures in software to create HDR or exposure-blended images (more on which below). How it works Depending on what mode you’re shooting in, the bracketing effect will be applied to different settings; if you’re in aperture-priority (A or Av), the shutter speed will be raised or Software skills Exposure blending in Photoshop Another reason to bracket shots is to blend exposures; this means taking the light parts from one and the dark parts from another to make a well-exposed scene. It’s a bit like using graduated neutral density filters when shooting, but with more control. You can blend exposures automatically (called tone-mapping or HDR processing), but here we’ll do it manually, which gives a more natural look. This technique uses the Layers palette in Adobe Photoshop or Elements software (you can apply the same principles to any program that uses layered images). We’re blending three images, but you can, of course, do more.

Use manual mode In manual mode (M), the shutter speed and aperture are set independently. To help, a +/- style exposure bar is displayed in the viewfinder or on screen, showing you how close to the camera’s metered exposure you are. This is a very accurate route to finding the best exposure, but it takes time and a tripod if merging shots. One consequence, as with compensation, is subject movement.

Use Auto Exposure Bracketing (AEB)

Many cameras have Auto Exposure Bracketing (AEB) allowing three, five, seven or even nine shots at different exposures. Dial in the number of frames, the amount of exposure adjustment between shots, press the release (several times in single frame advance) and a sequence is captured – if continuous drive is set the camera stops after the bracket. AEB is quick so the camera can be handheld, even for merging exposures.

+1.0 stop (1/30sec at f/16, ISO 100)

-1.0 stop (1/125sec at f/16, ISO 100)

(1/60sec at f/16, ISO 100)

lowered tomake exposures lighter or darker. If you’re in shutter-priority (T or Tv), the aperture will open or close to make the images lighter or darker. If you’re in program (P), both may change.

Most of the time, it’s best to shoot bracketed exposures in aperture priority, so that the depth-of-field in the image doesn’t change. For the same reason, you should keep the focus in the same place for each shot.

What about shooting in Raw? As Raw provides an exposure safety net, why would you still need to shoot bracketed? Well, changing the exposure of a Raw works fine up to a point, but beyond a certain level you’ll start to lose picture quality. You might also find very bright or dark areas are beyond processing control, with something like bright clouds remaining over-exposed no matter what you do. So, if you want to guarantee the highest quality, it’s advisable to shoot in Raw and still bracket the exposures; this will take more space on your card, but it’s worth it.

NextMonth Sharpen your focus

Final image

1. Stack the images In Photoshop or Elements, open the images to blend. Starting with the ‘middle’ exposure, go to Select > All, then Edit > Copy. Close this shot down and find the lightest version, then go to Edit > Paste. Open the Layers palette (Window > Layers) and you’ll now see a Background Layer (the lightest exposure), and Layer 1 (the middle exposure). Repeat this with the dark exposure, so you end up with three layers.

2. Blend the Layers In the Layers palette, click the top layer (Layer 2, the darkest exposure), then click the Add Layer Mask icon. Pick the Brush tool (B) and set it to black (D). You can now paint onto the image to reveal the layer below, so anywhere you paint you’ll see the lighter (‘middle’) exposure. It helps to paint with a soft-edged brush, and using a low Opacity, for a smoother transition, both of which you can set in the Options bar.

3. Finish the blend When you’re done blending Layer 1 and 2, repeat the process with Layer 1 and the Background, revealing the lightest tones from your bracketed sequence. If you make a mistake, or want to tone down the lightest area, like the house above, click on the Layer Mask and paint white (press X to switch the colours over). Go to Layer > Flatten Image and File > Save As…, so you can save the final picture under a new name.

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